I would guess that the name on Unique , or the name on Keyref,
would be reported in the PSVI if the instance document violated
the Unique-constraint or there was a mismatch between the
sections of the instance document selected by a particular
keyref (referencing the sections of the instance document
selected by its corresponding key).
Bob
Bob Schloss
Extensible Technologies, Next Gen Web group
IBM Thomas J. Watson Research Center